1. Field of the Invention
The present invention relates to a self-cutting dowel including a dowel rod having a head portion which widens in a setting direction, and a sleeve displaceable along the dowel rod and having, at its end adjacent to the head portion a plurality of expansion tabs separated by longitudinal slots, with the sleeve being displaceable onto the head portion upon radial expansion of the expansion tabs, and with the sleeve being provided with at least one cutter for forming an undercut in a ground during a dowel setting process, upon rotation of the sleeve.
2. Description of the Prior Art
In anchoring technology, it is often necessary to form connections which are expansion pressure-free to the greatest possible extent. In particular, with small edge and axis distances, the anchoring with conventional expansion dowels can result in fracture or even in stratification of the subsoil or the ground. To prevent this, there are provided anchoring systems in which a special connection or anchoring element is form-lockingly anchored in a receiving bore. To this end, a cylindrical receiving bore is provided at a predetermined depth with an undercut. An anchoring element, which is inserted in the pre-formed bore, includes an anchor rod provided with a head portion widening in a setting direction and extending through a bore of an expansion sleeve which is displaced over the anchor rod. The sleeve is provided with expansion segments which expand into the undercut as a result of a relative movement of the sleeve and the anchor rod.
For forming the undercut in most cases a special tool is required, which includes an abrasive cutter which is eccentrically rotated in the receiving bore and with which the undercut in the receiving bore is milled out. Also are known self-cutting dowels which automatically form an undercut during a setting process. Such a self-cutting dowel is disclosed in U.S. Pat. No. 4,702,654. The self-cutting dowel, which is disclosed in U.S. Pat. No. 4,702,654, has a sleeve provided at its leading, in the setting direction, end with expansion tabs which extend from a plastically deformable hinge toward a widening conical head portion at the leading end of the anchor rod. The expansion tabs expand radially over the head portion, which is supported on the bottom of the receiving bore, upon displacement of the sleeve. The expansion tabs are equipped with pin-shaped cutters which are inserted into the outer surface of the expansion tabs. During rotation of the sleeve, the cutters, which project beyond the sleeve circumference, mill an undercut in a receiving bore upon expansion of the expansion tabs. The setting process of the dowel ends when the sleeve has been displaced axially by a required amount, and the expansion tabs have expanded by a predetermined extent.
The setting of the known self-cutting dowel is effected with a rotary percussion tool for percussive-rotably pushing the sleeve over the conically widening head portion. At that, substantially, only the percussion components of the tool are used effectively. In particular, upon encounter with metal, this leads primarily to compression of the encountered metal and, therefore, this known dowel often cannot completely expand. Moreover, the cutting pins, which are provided in the outer surfaces of the expansion tabs can become loose and fall out because of a high axial load resulting from axial percussion during the setting process.
Accordingly, an object of the present invention is to eliminate the drawbacks of the prior art dowels. A self-cutting dowel should be provided with which an undercut in a cylindrical bore can be effectively formed. The self-cutting dowel should permit a contact with a reinforcing metal. The danger of losing the cutting elements, which are provided on expansion tabs and with which an undercut is formed, should be eliminated.